You're now prepared for Google's system design round.
Start with requirements. Spend minutes clarifying scale, features, and constraints before drawing anything.
Think in layers. Clients → load balancers → application → data stores. Label every arrow.
Know Google infrastructure. Borg, Bigtable, Spanner, Maglev, MapReduce. Reference these when they fit.
Trade-offs matter. Consistency vs availability, latency vs throughput, simplicity vs scalability. Always discuss alternatives.